Wrist pin construction



Dec. 16,1941.

E. IGRIEISHABER 2,

WRIST PIN CONSTRUCTION Filed July 10, 1939 I 3 Sheets-Sheet l 6mm BB J(Ittornegs Dec. 16, 1941. E. GRIESHABER WRIST PIN CONSTRUCTION FiledJuly 10, 1939 3 Sheets-Sheet 2 Patented Dec. 16, 1941 WRIST PINCONSTRUCTION Emil Grieshaber, Milwaukee, Wis., assignor to NordbergManufacturing Company, Milwaukee, Wis., a corporation of WisconsinApplication July 10, 1939, Serial No. 283,689 6 Claimsc1. 309-15) Thisinvention relates to reciprocating engines and particularly to pistonand wrist-pin constructlons intended primarily for use in Diesel en-Engines of this type have commonly been constructed with trunk pistons,in which the wrist pin is mounted in the piston proper. In such case,the piston performs also the functions of a. cross-head. In some cases,however, it is desirable to use a cross-head and guides distinct fromthe piston. The wrist pin constructions heretofore used for these twotypes of engine have been quite distinct, each being affected markedlyin design by the environment in which it is used.

The present invention is based on the concept that substantialmanufacturing economies can be eflfected when a manufacturer producesboth types of engine, by producing a standardized wrist pin constructioncapable of use with either type of engine. To do so is not a simpleproblem, because loads are heavy, the space limitations are severe(particularly in a. trunk piston), accessibility is essential, and meansmust be provided to supply through the wrist pin the cooling fluid (oil)required by the piston head. bviously, a heavily loaded wrist pin mustbe manufactured with precision and hence isan expensive component.Standardization of design thus results in unusual savings of cost andreduces the risk of failur because the performance of a standardizeddesign is predictable after adequate standardizing tests.

A preferred embodiment as applied to trunk pistons and to cross-headswill now be described by reference to the accompanying drawings, inwhich:

Figure 1 is an axial section through a trunk piston having the inventionincorporated. The plane of section is on the axis of the wrist pin.

Figure 2 is a similar section, the plane of section being normal to theaxis of the wrist pin.

Figure 3 is a section on the line 3-3 of Figure 1.

Figure 4 is a section on the line 44 of Figure 2.

Figure 5 is a section on the line 5-5 of Figure 1.

and connected piston. The wrist pin and connecting rod are identicalwith corresponding parts in Figures 1-6. I v

Figure 9 is a section (drawn on a somewhat enlarged scale) showing thepiston and wrist pm of Figure 8. The section is on the plane common tothe axis of the piston and the axis of the wrist pin.

Referring first to Figures 1 to 7, inclusive, the.

trunk piston is comprised of two major components, a head portion II,and a main sleeve portion l2, the head portion ll having ring grooves l3for the usual piston rings, and the sleeve portion having grooves M forother rings which usually are oil scraping rings.

A circular shoulder is formed at l5 to center the head and the sleeve,and these are held to- Figure 6 is a perspective view of the wrist pin.

gether by six studs it, two of which appear on the plane of section ofFigure 2. These studs are threaded into the head, extend through athickened portion of the sleeve, and their ends are exposed in pocketsl1. Two of these pockets appear in Figure 2, and all are clearly shownin Figure 4.

Within each pocket, a main nut l8 and a check nut is are applied to thestuds. Since the piston is single acting, the load carried by the studsis not great.

Mounted in under-cut grooves in the circumference of the sleeve, thereare wearing rings indicated generally at 2|, the provision of such ringsbeing standard construction.

Extending across the sides of the interior of the sleeve l2, and boundedby parallel secant lines, are two lugs 22 against which the wrist pinindicated generally by the numeral 23 seats. These lugs are flat ontheir lower faces and deliver thrust directly to flattened end portions24 of the wrist pin 23.

As is best shown in Figure 6, the wrist pin is of generally cylindricalcontour having a cylindrical journal or bearing surface indicated by thenumeral 25 in Figure 6 and having cylindrical ends conforming to theinterior circumference of the sleeve l2 and indicated in Figure 6 by thenumeral 26. In this way, a maximum seating area is secured at 24 withinthe limitation afforded by the internal dimensions of the sleeve l2. Thewrist pin is fastened to the lugs 22 by four studs 21. Construction ofthese'studs and the nuts mounted thereon can best be explained byreference to Figure 7.

Each stud has a threaded end 28 and a flange 29, the threaded portionentering threaded holes gin frame with cross-head guide, cross-head in acorresponding lug 22,'the flange 29 being seated in a countersink formedin the latter. Below the flange 29, each stud is relieved and thenenlarged at 3| to form a centering element for aligning the wrist pin.Below the portion 3| there is a short taper leading to reduced portion32. At a distance corresponding to the thickness of the end portion ofthe wrist pin, the stud is provided with threads 33 to receive a sleevenut 34. This nut is elongated as shown and terminates in a hexagonalwrench grip 35. Beyond the threads 33, the stud is further reduced andits end is threaded as indicated at 36 to receive a check nut 31. Theuse of the sleeve nut 34 brings the wrench grip 35 below the journalsurface 25 of the wrist pin and near enough to the lower end of theskirt I2 to permit it to be reached by an extension socket wrench. It iscontemplated that a special wrench will be made for tightening thesesleeve nuts and another for tightening the check nuts 31.

It will be observed that the studs are symmetrically arranged in theplane of the flattened end portions 24 and the arrangement is such as tofacilitate assembly and to avoid the transmission of bending stresses tothe studs.

The connecting rod which is generally indicated by the numeral 38 isprovided with a hearing bushing 39 pressed to place and held by a cateswith annular channel 60. Below this is a second annular channel 6|formed as an internal groove in the head II. The channel 6| and thelower portion of channel 66 encircle the enlargement 56 of the hollowfiller piece 55. The channel 60 communicates with the channel 6| bymeans of a tube 62 pressed into the intervening flange. The top of tube62 is located close to the top of channel 60 so that the spiral passageand passage 60 must substantially fill with oil befor dischargecommences.

The path of oil circulation is as follows:

Oil flows upward through the port 42 and through the port, 43, groove 44and port 46, to

' tube 52, t0 tube 5|.

staking screw 4i (see Figs. 1 and 2) Connecting rod 38 has an axial bore42 which, in accordance with past practice, receives oil under pressurefrom the crank pin (not shown). From the bore 42, a drilled port 43leads to a groove 44 in the inner face of the bushing 39, and thisgroove communicates with an axial bore 45 in the wrist pin 24 by meansof a drilled port 46. The ends of the bore 45 are closed by threadedplugs 41 (see Figs. 1 and 6).

As best illustrated in Figure 5, the holes formed in the ends of thewrist pin 24 to receive the studs 21 do not enter the bore 45. A drilledport 48 leads from the bore 45 and communicates with a drilled port 49in the left-hand lug 22 of Figure 1. A. drilled port similar to the port48, but larger, is formed in the other end of the wrist pin and extendsclear through the end of the pin. It is, however, isolated from the bore45 by tube 5|, pressed to place and making a fluid-tight connection withthe wrist pin. The tube 5I is clearly shown at th right of the wrist pinin Figure 1, and also in Figure 5. The tube 5i is in directcommunication with a tube 52 of the same diameter, pressed to place, inbores formed in the sleeve I2 (see Figure 1).

. Formed integrally with the sleeve I2 and extending upward from thebosses 22 is a conical barrier open at its center and indicated by thenumeral 53. Mounted on the upper margin of the barrier 53 and connectedthereto by machine screws 54 is a cup-shaped filler piece 55 having anenlarged upper end 55 and a diagonal tubular passage 51 formedintegrally therewith, and arranged as shown in Figures 1 and 2. Thisfiller piece coacts with flanges and ribs formed on the interior of headII, and with portions of sleeve I2 to form oil chambers and passagesthrough which oil is circulated.

The head ii is of generally cup-shaped con figuration and the enlargedhead 55 on the member 55 lies within the head II. On the inner face ofthe head II is a spiral baffle indicated at 58 and arranged to provide,in filler piece 55, a spiral passage 59 with theinner end of which thetubular duct 51 communicates. The spiral passage 59 at its outer endcommuniconjunction with the bore 45 of the wrist pin. Thence it flowsthrough the ports 46, 49 to the annular space 56 within the sleeve I2aroundthe lower portion of the filler 55. From this annular space, theoil flows through the tubular passage 51 to the inner end of the spiralpassage 59 and thence through the spiral passageto channel 60 throughthe tube 62, thence through channel 6| to the The tube 5| dischargesthrough the lower end of the piston directly into the crank case (notshown). It follows that the circulating oil not only lubricates thewrist pin but also flows through the upper part of the piston skirt andthen in a sinuous path through the piston head, ultimately dischargingback to the crank case from which the circulating oil is drawn.

In Figures 8 and 9, a modified construction is shown which, however,uses certain components used in Figures 1 and 2. Where the componentsare the same, the same reference numerals are used in Figures8 and 9.Other components are given distinctive numerals. The cylinder headportion II is the same as in Figures 1 and 2 and is provided with ringgrooves I3 as before. It has the annular groove passage 6|, channel 60,spiral rib 56, spiral passage 59, and connecting tube 62. These'passagesare completed by an inserted cup I56 which performs th same function asthe enlarged head 56 shown in Figures 1 and 2.

The sleeve portion II2 of the piston is ribbed on its inner surface asindicated at H4 and has no ring grooves. It is connected by the studsII6 (see Fig. 8) with a cross-head indicated at H. 'I'he*crcss-head isguided in the cross-head guide 12 which is carried by a portion of theengine frame 13. The particular form of the cross-head guide and engineframe are not material, but are clearly indicated in the drawings.

The cross-head H is formed with two parallel shoulders I22, functionallysimilar to the lugs 22 in Figures 1 and 2. Mounted against these lugs isthe wrist pin 23 which is identical with the wrist pin shown in Figures1 and 2. It is associated with connecting rod 36 which may be identicalwith and, in any event, is functionally identical with the connectingrod shown in Figures 1 and 2. This being the case, there is an axialbore 42, port 43, groove 44, axial bore 45', port 46, and plugs 41, port48 and inserted tube 5I. is functionless, as hereafter explained.

The port 46 communicates with a port I49 in the cross-head, and this isconnected by a pipe I51, to a passage leading through cup I56 to theinner end of the spiral passage 59 in head I I.

The discharge port .from channel 6I which in the embodiment of Figures 1and 2 communicates with the pipe 52, in Figures 8 and 9 communicateswith a port in the sleev II2 with which In this environment, however,the tube 5| is connected a pipe I52. The lower end of pipe I52communcates with a passage I53 in the second lug I22 on the cross-head.The lower end of the port I53 is closed by a screw plug I54,

and the port has a lateral discharge leading to' an elbow I55.

The elbow I55 carries a discharge pipe I56 whose end is housed withinthe pipe I51 leading to the oil-sump of the engine.

It follows that assuming a cylinder bore of given size, the piston headcomponent, the wrist pin, and, in certain cases, the connecting red, areinterchangeable and may be manufactured to a single standard for use ineither type of engine.

It is deemed unnecessary to trace the circulation of oil with referenceto Figure 9 because it follows very closely the circulationcharacteristics of Figures 1 and 2, and the only difference is that theris no chamber corresponding to the chamber 50 (Figs. 1 and 2) so thatthe piston is not charged with oil through any portion of the skirt II2.Instead, the cooling circulation is confined to the head I I.

The purpose of the design is to secure the maxi- 'mum practicableseating area at 24, for a wrist pin of a maximum practicable diameter.On these dimensions the trunk-type piston imposes the closestlimitations, but since the effective piston area is the same whether ornot a crosshead is used, any wrist pin which will withstand the stressesencountered in one type of engine will be adequate to withstand similarstresses encountered in the other. Y

The studs 32 hold the parts in assembled relation, but since the piston.is single-acting, the studs never transmit the working thrust developedupon the piston head.

The use of the elongated sleeve nuts 34 makes these accessible, even inthe trunk piston, and ,it is highly advantageous to be able to use thesame studs, nuts andvcheck nuts in both types of engine, because, as inthe case of the wrist pin, standardization results in predictableperformance.

When used with trunk pistons, the invention has the advantage that nopart of the wrist pin extends through sleeve I2, nor does it require anyopening to be formed in that sleeve. The wrist pin may be dismounted andreconnected while the piston is in the cylinder which is a greatadvantage from the maintenance standpoint, because it permits theconnecting rod to be dismounted without pulling the piston and permitsthe piston to be pulled through the head end of the cylinder withoutdismounting the connecting rod. This permits reduction in the height ofthe engine room, because it is necessary to provide space to pull onlythe piston, not as heretofore the piston and connecting rod.

The arrangement here disclosed to secure the cylinder whose diameter issomewhat less than i the diameter 'of the piston head and whose axis iscoincident with the axis of such head, the end portions of said wristpin being cut away to afford seats for engaging said parallel lugs, saidwrist pin having an oil passage leading through it from the journalsurface to one'of said seats in position to register with the passage inthe corresponding lug; threaded connections engaging saidlugs and theend of said pin; and a connecting rod including a bearing joumaled onsaid pin and having an oil passage leading to said bearingandcommunicating with the oil passage in said wrist pin 2. The" combinationof a trunk piston includ-' 'ing a head and a guiding sleeve forming areciprocating unit, there being an oil circulating passage in the headand wrist, pin supporting lugs in the sleeve, said lugs being formedwith passages which communicate with opposite ends of the passage in thehead; a wrist pin having a cylindrical journal at its mid-portion androunded ends which are portions of a ,right cylinder whose diameterapproximates the internal diameter of the sleeve with which it isco-axial, the end portions of said wrist pin being cut away to affordseats for engaging said lugs, said wrist pin having an oil passageleading through it from the journal surface to one of said seats inposiing a bearing journaled on said pin and having maximum possibledimensions of wrist pin within an oil passage leading to said bearingand communicating with theoil passage in the wrist pin. 3. A wrist pinfor use with pistons of the oil cooled type, comprising a member havinga cy1indrical journal for a connecting rod at its midportion and roundedends which ends are portions of a right cylinder whose diameter does notexceed the 'internal diameter of a trunk piston for which the pin issuited, and whose axis is perpendicular to the axis of said journal, theend portions of said member being cut away to parallel planessecant tosaid cylindrical ends to afford seats for mounting the member, saidmember having an oil passage leading through it from the journal surfaceto one of said seats, and a distinct oil passage leading through theother end from the other of said seats, each of said passagesterminating at the middle of the seat, and the pin having bolt holes,two in each seat located at opposite sides of the passage aforesaid.

'4. A wrist pin for use with pistons of the oil cooled type, comprisinga pin having a cylindrical /journal for a connecting rod at its midportion v I and rounded'ends, which ends are portions of a rightcylinder whose diameter does not exceed the internal diameter of thepiston for which the pin is suited and whose axis is perpendicular tothe axis of said journal, the end portions of said pin being shoulderedto form seats for mounting said pin in such piston, said pin having anoil'passage leading through it from its journal surface to one ofsaidseats, said'passage including'a bore substantially coaxial with'thejournal surface of the pin and extending substantially from end to endof the pin but closed at each end, the pin having bolt holes out ofcommunication with said axial bore.

5. The combination of a trunk piston comprising a head formed with ahead cooling passage for oil, and a guiding sleeve having wrist pinsupporting lugs wholly internal to the sleeve, one of said lugs beingprovided with a port connected with the entrance end of said coolingpassage in the head; a wrist pin wholly internal to said sleeve andhaving seats at its ends for engaging said lugs, said pin having ajournal for the connecting rod intermediate said lugs, said wristpin'having an oil passage leading through it from the surface of thejournal to that seat which engages the ported lug, said passage in thewrist pinincluding a chamber which extends nearly but not quite from endto end of the wrist pin; means for rigidly connecting the ends of saidpin to the lugs within said skirt; a connecting rod including a bearingjournaled on said pin; and means for supplying oil to the chamber in thewrist pin.

6. The combination or a trunk piston comprising ahead formed with a headcooling passage for oil, and a guiding sleeve having wrist pinsupporting lugs wholly internal to the sleeve, said lugs being providedwith ports connected with the respective ends of .the cooling passage inthe head; a wrist pin wholly internal to said sleeve and having seats atits ends for engaging said lugs, said pin having a journal for theconnecting rod intermediate said lugs, said wrist pin having an oilpassage leading through it from the surface of the journal to one ofsaid seats to communicate with the port therein, said passage in thewrist pin including a chamber which extends nearly but not quite fromend to end or the wrist pin and the wrist pin having a second passage.distinct from the one just defined which communicates with the passagein the other lug; means for rigidly connecting the ends of said pin tothe lugs within said skirt, and a connecting 'rod including a bearingjournaled on said pin and having an oil passage leading to said bearingand communicating with the oil passage which leads from the surface ofthe journal.

' EMIL GRIESHABER.

